JP2014110144A - Connection structure of oxide superconductive conductor and superconductive apparatus provided therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the connection structure of oxide superconductive conductors in which deterioration in the characteristics of oxide superconductive layers is not caused even if bending stress is applied to connected parts, and a superconductive cable and a superconductive apparatus provided with the structure.SOLUTION: This invention is characterized in that, in a structure where a tape-shaped base material is laminated with an intermediate layer, oxide superconductive layers and metal stabilization layers, the edge parts of the first and second superconductive conductors are mutually adjacent in such a manner that the metal stabilization layers are mutually superimposed, and the superimposed parts of the metal stabilization layers are joined with conductive joining materials having a Young's modulus of less than 41.4×10N/m.

Description

  The present invention relates to an oxide superconducting conductor connection structure and a superconducting device including the same.

It is desired to provide a superconducting conductor or a superconducting coil for power supply by processing a RE-123 series oxide superconductor (REBa ₂ Cu ₃ O _7-X : RE is a rare earth element including Y) into a wire. Yes. As an example of the structure of an oxide superconductor, an intermediate layer with good crystal orientation is formed on the surface of a metal tape substrate by ion beam assisted vapor deposition (IBAD method), and the oxide superconductor is formed on the intermediate layer by film formation. An oxide superconductor having a structure in which a layer is formed and an Ag protective layer and a Cu stabilizing layer are laminated on the surface has been developed.

  A conventional RE123-based oxide superconducting conductor employs a structure in which a thin Ag protective layer is formed on an oxide superconducting layer and a thick stabilization layer made of Cu is formed thereon. The protective layer of Ag is also provided for the purpose of adjusting fluctuations in the amount of oxygen when the oxide superconducting layer is subjected to oxygen heat treatment, and the Cu stabilizing layer is normally used when the oxide superconducting layer is in a superconducting state. It is provided in order to function as a bypass for commutating the current of the oxide superconducting layer when attempting to transition to the conductive state.

By the way, in order to apply such a superconducting conductor to a practical device, a technique for connecting the superconducting conductor has been studied.
When connecting RE123-based oxide superconducting conductors, since the oxide superconducting layer is formed on one side of the tape base as described above, the oxide superconducting layers face each other and are connected by soldering or the like. There is a need.
As an example of a method and a connection device for connecting oxide superconducting conductors, the ends of flat oxide superconducting conductors can be overlapped with each other, a solder material can be sandwiched therebetween, pressurized from above and below, and heated. A connecting device including a pair of pressure heating plates is known (see Patent Document 1).
This connecting device has a clamping mechanism on both sides of the pressure heating plate, the ends of the oxide superconducting conductor temporarily held by the clamping mechanism are sandwiched by the pressure heating plate, the solder material is melted, solidified, and abutted It is provided as an apparatus capable of soldering the ends of a superconducting material.

JP 2011-003382 A

If a structure in which the ends of the oxide superconducting conductor are overlapped and soldered is employed, the front and back of the superconducting conductor are reversed at the connecting portion, and various problems occur in practice. Therefore, the oxide superconducting conductors to be connected are arranged adjacent to each other in the same direction, and the connecting oxide superconducting conductors facing the ends of the adjacent superconducting conductors are bridged and soldered. The structure to attach is known.
The solder material provided at the connecting portion of the oxide superconducting conductor is generally made of lead-free type tin, and includes a soldered joint formed by melting and solidifying the solder material made of tin. Yes.
However, when the oxide superconducting conductor subjected to soldering is applied to a superconducting coil, the superconducting conductor is wound around a winding drum to form a coil, so that bending stress at the time of winding acts on the soldered portion. As a result of various tests conducted by the present inventor, even when there is no deterioration in the characteristics of the oxide superconducting conductor itself to which bending stress is applied, there is a possibility that the superconducting characteristics may be deteriorated if there is a connection portion with a soldered portion. found. The reason for this is that when bending stress is applied to the soldered part, the oxide superconducting conductor itself is tape-like and flexible, but the hard soldered part locally applies stress to the surrounding oxide superconducting layer. It can be presumed that this is caused by the addition.

The present invention has been made in view of such a conventional situation, and by reducing the Young's modulus of the joint portion by a conductive joint material such as solder to some extent, even if bending stress acts on the joint portion, the oxide An object of the present invention is to provide a connection structure for oxide superconducting conductors that does not cause deterioration of characteristics of the superconducting layer.
Another object of the present invention is to provide a superconducting cable to which the above connection structure is applied, or a superconducting device such as a superconducting coil or a superconducting fault current limiter.

In order to solve the above-mentioned problems, the present invention provides a structure in which the end portions of the first and second superconducting conductors having a structure in which an intermediate layer, an oxide superconducting layer, and a metal stabilizing layer are laminated on a tape-like base material are mutually metallic. The stabilization layers are adjacent to each other by being overlapped, and the overlapped portion of the metal stabilization layer is bonded by a conductive bonding material having a Young's modulus of less than 41.4 × 10 ⁹ N / m ² .
Since the metal stabilizing layers are connected to each other with a conductive bonding material having a Young's modulus of less than 41.4 × 10 ⁹ N / m ² , the stress concentration on the oxide superconducting layer around the connection portion even if bending stress acts on the connection portion It is possible to provide a connection structure with less deterioration of superconducting characteristics.

In order to solve the above-mentioned problems, the present invention provides a structure in which the end portions of the first and second superconducting conductors having a structure in which an intermediate layer, an oxide superconducting layer, and a metal stabilizing layer are laminated on a tape-like base material are mutually metallic. The stabilization layers are adjacent to each other on the same side of the substrate, and the ends of these adjacent metal stabilization layers are laminated on the tape-shaped substrate with the intermediate layer, oxide superconducting layer, and metal stabilization layer. A connection structure of oxide superconducting conductors connected by a third superconducting conductor having the structure described above, wherein the ends of the metal stabilizing layers of the adjacent first and second superconducting conductors are connected to each other. A metal stabilizing layer is applied, and the metal stabilizing layer of the first and second superconducting conductors and the metal stabilizing layer of the third superconducting conductor are joined by a conductive bonding material, and the conductive this Young's modulus of the bonding material is less than 41.4 × ¹⁰ 9 N / ^{m 2} The features.
Since the metal stabilization layers of the first and second superconducting conductors are connected to the metal stabilization layer of the third superconducting conductor with a conductive bonding material having a Young's modulus of less than 41.4 × 10 ⁹ N / m ² , Even if a bending stress is applied to the first and second superconducting conductors applied to a structure in which the first and second superconducting conductors are coiled, the first, second and third superconducting conductors are connected. The stress acting on the oxide superconducting layer around the portion can be reduced, and a connection structure with little deterioration of superconducting characteristics can be provided. When the Young's modulus of the conductive bonding material for bonding the first, second, and third superconducting conductors is less than 41.4 × 10 ⁹ N / m ² , the entire conductive bonding material when bending stress acts There is a high probability that the conductive bonding material is partially bent, and the possibility of locally applying stress to the oxide superconducting layer is reduced.

The present invention is a superconducting device provided with the oxide superconducting conductor junction structure described above.
In the superconducting equipment such as superconducting cables, superconducting coils, and superconducting fault current limiters, the superconducting characteristics of the superconducting devices are deteriorated even if stress such as bending acts on the connecting part between the oxide superconducting conductors. It is possible to provide a superconducting device that is unlikely to occur.

In the present invention, the metal stabilizing layers of the superconducting conductors are connected to each other by a conductive bonding material having a Young's modulus of less than 41.4 × 10 ⁹ N / m ² . The stress concentration on the oxide superconducting layer can be reduced, and a connection structure with little deterioration of superconducting characteristics can be provided.
The present invention also provides a conductive bonding material having a Young's modulus of less than 41.4 × 10 ⁹ N / m ² between the metal stabilizing layers of the first and second superconducting conductors and the metal stabilizing layer of the third superconducting conductor. Even if a bending stress is applied to the first, second, and third superconducting conductors by applying to the structure in which the first and second superconducting conductors are coiled, etc., the first and second superconducting conductors are connected. 2. It is possible to reduce stress concentration on the oxide superconducting layer around the connection portion of the third superconducting conductor, and to provide a connection structure with little deterioration of superconducting characteristics.

It is a partial section perspective view showing an example structure of an oxide superconducting conductor applied to a connection structure concerning the present invention. It is sectional drawing which shows 1st Embodiment of the connection structure of the oxide superconductor shown in FIG. FIG. 3 is a perspective view showing an example of an oxide superconducting cable to which the connection structure shown in FIG. 2 is applied. It is a perspective view which shows an example of the superconducting fault current limiter provided with the module for oxide superconducting fault current limiters to which the connection structure shown in FIG. 2 is applied. FIG. 5A shows an example of a superconducting motor provided with an example of an oxide superconducting coil to which the connection structure shown in FIG. 2 is applied. FIG. 5A is a partially sectional perspective view, and FIG. is there. FIGS. 6A and 6B show another example of an oxide superconducting coil to which the connection structure shown in FIG. 2 is applied. FIG. 6A is a perspective view of a laminated coil, and FIG. It is sectional drawing which shows 2nd Embodiment of the connection structure of the oxide superconductor shown in FIG. It is a graph which shows the bending test result in an Example.

Hereinafter, a first embodiment of a connection structure of oxide superconducting conductors will be described in detail with reference to the drawings. The present invention is not limited to the embodiments described below. In addition, the drawings used in the following description may show the main parts in an enlarged manner for convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of the respective components are the same as the actual ones. Not always.
As shown in FIG. 1, the oxide superconducting conductor 1 used in the connection structure of the present embodiment has an intermediate layer 5, an oxide superconducting layer 6, and a first metal on one surface (surface) of a tape-like substrate 2. A laminated body 9 is formed by laminating the stabilizing layer 7, and the second metal stabilizing layer 8 covers almost the entire circumference of the laminated body 9. In the embodiment shown in FIG. 1, the second metal stabilization layer 8 does not cover the entire circumference of the laminate 9, but covers almost the entire circumference of the laminate 9. In FIG. 2, only a part of the second metal stabilizing layer 8 is not covered, and this part is separately covered with the conductive bonding material layer 11. In this embodiment, the second metal stabilizing layer 8 is provided so as to cover the entire circumference of the laminate 9 except for the central portion on the back surface side of the substrate 12, and the conductive bonding material layer 11 is formed of the substrate 2. The second metal stabilizing layer 8 is deposited between the end edges so as to fill in the space between the end edges of the second metal stabilizing layer 8 at the center in the back surface width direction. Although omitted in FIG. 2, a conductive bonding material layer such as solder is formed on almost the entire inner peripheral surface of the second stabilization layer 8. It is preferable that the second stabilization layer 8 is in close contact with the substantially entire circumferential surface of the laminate 9 via a conductive bonding material layer.

The connection structure of the oxide superconducting conductor of this embodiment is applied when two oxide superconducting conductors 1 having the structure shown in FIG. 1 are connected.
FIG. 2 shows a first embodiment of a connection structure, in which two oxide superconducting conductors 1 are adjacent to each other with a gap d between them and the first metal stabilizing layer 7 is formed. Are arranged in a straight line on the same side with respect to the base material 2, and a third oxide superconductor 13 is attached so as to bridge between adjacent ends of the oxide superconductors 1 and 1. Is provided. In the present embodiment, one (left side in FIG. 2) of the oxide superconductors 1 and 1 to be connected for convenience is referred to as the first oxide superconductor 1 and the other (right side in FIG. 2) is the second. The oxide superconductor 1 is called.
The third oxide superconducting conductor 13 is a short tape-shaped oxide superconducting conductor having the same structure as the first and second oxide superconducting conductors 1 described above. That is, the intermediate layer 5, the oxide superconducting layer 6, and the first metal stabilizing layer 7 are laminated on the base material 2 to form a laminated body 9, and the second metal is formed almost entirely on the laminated body 9. Although it is configured to be covered with the stabilization layer 8A, it is made of an oxide superconductor having a short length, for example, about several centimeters to several tens of centimeters, specifically about 1 cm to 20 centimeters depending on the connection target.

  The third oxide superconducting conductor 13 has a first metal stabilizing layer 7 provided on the inner side thereof on the first stabilizing layer 7 side of the first and second oxide superconducting conductors 1, 1. The second metal stabilization layer 8A is placed along the second stabilization layer 8 of the first and second oxide superconducting conductors 1 and 1 and a conductive junction such as solder interposed between them. The material 15 is connected to the first and second oxide superconductors 1 and 1.

In the first to third oxide superconducting conductors 1, 1, and 13, the base material 2 may be any material that can be used as a substrate for a normal oxide superconducting conductor, and has a flexible tape shape. It is preferable that it is made of a heat-resistant metal. Among heat-resistant metals, nickel (Ni) alloys are preferable. Among them, if it is a commercial product, Hastelloy (trade name, manufactured by Haynes) is suitable, and the amount of components such as molybdenum (Mo), chromium (Cr), iron (Fe), cobalt (Co) is different, Hastelloy B, Any kind of C, G, N, W, etc. can be used. Further, an oriented metal substrate in which a texture is introduced into a nickel alloy or the like may be used as the base material 2, and the intermediate layer 5 and the oxide superconducting layer 6 may be formed thereon.
What is necessary is just to adjust the thickness of the base material 2 suitably according to the objective, Usually, it is preferable that it is 10-500 micrometers, and it is more preferable that it is 20-200 micrometers.

The intermediate layer 5 functions as a buffer layer that alleviates the difference in physical properties (thermal expansion coefficient, lattice constant, etc.) from the oxide superconducting layer 6 formed thereon, and the physical properties are the same as those of the base material 2 and oxidized. A metal oxide showing an intermediate value with the physical superconducting layer 6 is preferable. Specifically as the intermediate layer _{5, Gd 2 Zr 2 O 7} , MgO, ZrO 2 -Y 2 O 3 (YSZ), SrTiO 3, CeO 2, Y 2 O 3, Al 2 O 3, Gd 2 O 3, Examples thereof include metal oxides such as Zr ₂ O ₃ , Ho ₂ O ₃ , and Nd ₂ O ₃ , and those formed by IBAD method (ion beam assisted deposition method) to adjust the crystal orientation are preferable.
The intermediate layer 5 may be a single layer or a plurality of layers. In the case of a plurality of layers, the outermost layer (the layer closest to the oxide superconducting layer 6) has at least good crystal orientation. preferable. For this reason, after forming a first alignment layer with good crystal orientation by the IBAD method, a second alignment layer capable of epitaxial growth is laminated on the first alignment layer by a film forming method such as sputtering. It can also be a layered structure. In the case of a multilayer structure, the first alignment layer and the second alignment layer may be layers made of the same material or layers made of different materials.
The intermediate layer 5 may have a multi-layer structure in which a bed layer is interposed on the substrate 2 side. The bed layer is arranged as necessary, and is made of yttria (Y ₂ O ₃ ), silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ , also referred to as “alumina”), or the like. The thickness of the bed layer is, for example, 10 to 200 nm.

Further, in the present invention, the intermediate layer 5 may have a multi-layer structure in which a diffusion prevention layer and a bed layer are laminated on the base material 2 side. In this case, a diffusion preventing layer is interposed between the base material 2 and the bed layer. The diffusion prevention layer has a single-layer or multi-layer structure made of silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ), or rare earth metal oxide, and has a thickness of, for example, 10 to 400 nm. .
The intermediate layer 5 may have a multilayer structure in which a cap layer is further laminated on the metal oxide layer formed by the IBAD method. The cap layer has a function of controlling the orientation of the oxide superconducting layer 6 and achieving a good crystal orientation like a single crystal. Capping layer is not particularly limited, specifically as _{preferred, CeO 2, Y 2 O 3} , Al 2 O 3, Gd 2 O 3, ZrO 2, Ho 2 O 3, Nd 2 O 3, LaMnO 3 Etc. can be illustrated. When the material of the cap layer is CeO ₂ , the cap layer may contain a Ce—M—O-based oxide in which part of Ce is substituted with another metal atom or metal ion.

The oxide superconducting layer 6 can be widely applied to an oxide superconductor having a generally known composition, such as REBa ₂ Cu ₃ O _y (RE is Y, La, Nd, Sm, Er, Gd, etc. And a material such as Y123 (YBa ₂ Cu ₃ O _y ) or Gd123 (GdBa ₂ Cu ₃ O _y ). Further, other oxide superconductors, for _{example, Bi 2 Sr 2 Ca n-} 1 Cu n for _{O 4 + 2n + δ} becomes may be used in compositions such as those made of other oxide superconductors having high critical temperatures representative Of course. The oxide superconducting layer 6 has a thickness of about 0.5 to 5 μm and preferably a uniform thickness.

The first metal stabilizing layer 7 is made of a metal material that has good conductivity, such as Ag or an Ag alloy, has low contact resistance with the oxide superconducting layer 6, and is compatible.
The reason why the first metal stabilizing layer 7 is made of Ag is that it has a property of making it difficult to escape the doped oxygen from the oxide superconducting layer 6 in the annealing step of doping the oxide superconducting layer 6 with oxygen. Can be mentioned. In order to form the first metal stabilizing layer 7 made of Ag, a film forming method such as a sputtering method is adopted, and the thickness thereof is set to about 1 to 30 μm.

The second metal stabilizing layers 8 and 8A are made of, for example, a highly conductive metal material. When the oxide superconducting layer 6 attempts to transition from the superconducting state to the normal conducting state, the first stabilizing layer 7 is formed. At the same time, the oxide superconducting layer 6 functions as a bypass through which current flows.
The metal material constituting the second metal stabilization layer 8 or 8A is not particularly limited as long as it has good electrical conductivity, but copper, brass (Cu—Zn alloy), Cu—Ni alloy, etc. It is preferable to use a material made of a relatively inexpensive material such as a copper alloy or stainless steel. Among them, copper is preferable because it has high conductivity and is inexpensive. When the oxide superconducting conductor 1 is used for a superconducting fault current limiter, the second metal stabilizing layers 8 and 8A are made of a resistance metal material, and a Ni-based alloy such as Ni—Cr can be used.

The conductive bonding material 15 is made of solder having a Young's modulus of less than 41.4 GPa (41.4 × 10 ⁹ N / m ² ). As an example, indium solder having a Young's modulus of 10.8 GPa (10.8 × 10 ⁹ N / m ² ) is used.
In addition, Sn—Pb solder (Young's modulus: 22 GPa), Sn—Ag—Cu solder (Young's modulus: Young's modulus) as a conductive bonding material having a Young's modulus of less than 41.4 GPa (41.4 × 10 ⁹ N / m ² ). 31 GPa), Sn-Ag-Cu solder (Young's modulus: 36 GPa), Sn-Bi-Ag solder (Young's modulus: 24 GPa), eutectic solder (Pb37Sn63: Young's modulus 19.27 GPa), or the like can be used.

In order to manufacture the oxide superconducting conductors 1 and 13 having the structure shown in FIG. 1, the intermediate layer 5, the oxide superconducting layer 6, and the first metal stabilizing layer 7 are formed on the base material 2 by the various film forming methods described above. A tape-shaped laminate 9 is prepared, a metal tape having a necessary width is arranged along the laminate 9, and the second tape is bent by roll forming using a pressure heating roll. Thus, the superconducting conductors 1 and 13 can be formed by forming the metal stabilizing layer 8 or the second metal stabilizing layer 8A.
In addition, when covering the laminated body 9 with the 2nd stabilization layer 8 and 8A, it is preferable to use what formed the solder preliminary layer by plating on the back surface side of the metal tape. These solder preliminary layers can be made to have a thickness of about 2 μm to 6 μm by solder plating or the like.
As a solder material constituting the solder preliminary layer, for example, lead-free made of an alloy containing Sn as a main component such as Sn, Sn—Ag alloy, Sn—Bi alloy, Sn—Cu alloy, Sn—Zn alloy, etc. Examples thereof include solder, Pb—Sn alloy solder, eutectic solder, low temperature solder, and the like, and these solders can be used alone or in combination. In the solder preliminary layer, the material used for forming the conductive bonding material 15 may be applied. In addition, since the solder spare layer applied to the back side of the second metal stabilizing layers 8 and 8A is formed thinner than the conductive bonding material 15 described above, these solder spare layers are formed by bending the oxide superconductor 1. Since the influence upon bending is small, a normal solder material can be used, but the above-described solder having a Young's modulus of less than 41.4 GPa (41.4 × 10 ⁹ N / m ² ) may be used.

In the connection structure shown in FIG. 2 obtained as described above, the Young's modulus of 41.4 is applied to the metal stabilizing layer 8A of the third superconducting conductor 13 between the metal stabilizing layers 8 of the first and second superconducting conductors 1. Since the conductive bonding material 15 is less than × 10 ⁹ N / m ² , the first and second superconductivity are applied to a structure in which the first and second superconducting conductors 1 and 1 are wound around a winding drum. Even when bending stress is applied to the conductor 1, the stress acting on the oxide superconducting layer 6 around the connecting portion of the first, second, and third superconducting conductors 1, 1, and 13 can be reduced. It is possible to provide a connection structure with little deterioration of superconducting characteristics. If the Young's modulus of the conductive bonding material 15 for bonding the first, second, and third superconducting conductors 1, 1, and 13 is less than 41.4 × 10 ⁹ N / m ² , when bending stress acts There is a high probability that the entire conductive bonding material 15 is bent evenly, and there is less possibility that stress is locally applied to the oxide superconducting layer 6 when the conductive bonding material 15 is partially bent. On the other hand, if the conductive bonding material has a Young's modulus exceeding 41.4 × 10 ⁹ N / m ² , the hardness of the connection portion is high, so that the connection portion that is hard according to the curvature of the oxide superconductors 1 and 1 Is bent upward, and the bent connection portion partially applies stress to the upper oxide superconducting layer 6, and as a result, the oxide superconducting layer 6 at the position where the bending stress is partially received is subjected to a large stress. There is a possibility that the characteristics are greatly deteriorated. On the other hand, if the conductive bonding material 15 has a Young's modulus of less than 41.4 × 10 ⁹ N / m ² , it can be moderately soft and the concentration of bending stress can be alleviated. As a result, superconducting characteristics are hardly deteriorated. The Young's modulus of the conductive bonding material 15 is more preferably 11 GPa or less.

Since a gap d is provided between the first and second oxide superconducting conductors 1, 1, the first and second oxide superconducting conductors 1, 1 are wound when wound around a winding drum or the like. Interference between ends can be prevented. The gap d can be set to an arbitrary width in the range of several mm to several tens of cm according to the bending radius required when the oxide superconducting conductor 1 is bent.
Further, if Sn is used as the constituent material of the conductive bonding material 15, the heating temperature must be raised to the melting point of Sn or more at the time of connection, so the laminated body 9 is covered with the second metal stabilizing layer 8. In this case, the Sn of the solder preliminary layer used in this case reaches the melting point, and as a result, the molten Sn absorbs a part of Ag constituting the first metal stabilizing layer 7 and the first metal stabilization. The function of the layer 7 may be impaired. On the other hand, if the conductive bonding material 15 is made of indium solder, the heating temperature for connection can be made higher than the melting point of indium (about 156 ° C.) and lower than the melting point of Sn (about 232 ° C.). There is an effect that connection can be made without melting Ag on the surface of the first metal stabilizing layer 7.

The oxide superconducting conductor connection structure shown in FIG. 2 can be applied to, for example, the high-temperature superconducting cable 16 illustrated in FIG. The high-temperature superconducting cable 16 shown in FIG. 3 forms a superconducting layer 18 by arranging a plurality of layers of the oxide superconducting conductor 1 in a winding shape on the outer periphery of a former 17 provided at the center, and an insulating layer 19 and a superconducting layer on the outer periphery. A shield layer 20 and a protective layer 21 are formed to constitute a core cable 22, and the core cable 22 is accommodated inside a heat insulating pipe 23 with a gap for refrigerant circulation. The heat insulation pipe 23 has, for example, a double pipe structure including an inner pipe 23a and an outer pipe 23b, and a vacuum heat insulation layer 23c is formed between the inner pipe 23a and the outer pipe 23b. The superconducting shield layer 20 is configured by arranging the oxide superconducting conductor 1 in a multi-layer winding shape.
Since such a high temperature superconducting cable 16 is manufactured as a long cable, the oxide superconducting conductor 1 forming the superconducting layer 18 or the oxide superconducting conductor 1 constituting the superconducting shield layer 20 is used as another superconducting cable. Since a connection configuration is required, a structure in which the oxide superconducting conductor 1 shown in FIG. 2 is connected to another oxide superconducting conductor is applied.

The connection structure of the oxide superconducting conductor shown in FIG. 2 can be applied to, for example, the superconducting fault current limiter 99 shown in FIG.
In the superconducting current limiter 99 shown in FIG. 4, the oxide superconducting wire 1 having the connection structure shown in FIG. 2 is wound around a winding drum in a plurality of layers to form a superconducting current limiter module 90. The current limiting module 90 is stored in a liquid nitrogen container 95 filled with liquid nitrogen 98. Further, the liquid nitrogen container 95 is stored inside a vacuum container 96 that blocks heat from the outside.
The liquid nitrogen container 95 has a liquid nitrogen filling part 91 and a refrigerator 93 in the upper part, and a heat anchor 92 and a hot plate 97 are provided below the refrigerator 93.
The superconducting current limiter 99 has a current lead portion 94 for connecting an external power source (not shown) to the superconducting current limiter module 90.
When used as the superconducting fault current limiter module 90 of the superconducting fault current limiter 99 as described above, the oxide superconducting wire 1 has Ni—Cr as the second stabilizing layer 14 as described with reference to FIG. Use a high-resistance metal such as

2 is applied to, for example, a superconducting motor (superconducting device) 30 having the structure shown in FIG. A superconducting motor 30 shown in FIG. 5 includes a shaft-shaped rotor 32 rotatably supported in a cylindrical hermetic horizontally long container 31, and a cooling gas such as helium gas is supplied into the container 30. It is comprised so that it can supply to.
A plurality of superconducting coils 35 are attached to the periphery of the central portion of the rotating shaft 33, and a plurality of normal conducting coils are formed of copper coils supported on the inner wall side of the container 31 around the plurality of superconducting coils 35. 36 is arranged.
A plurality of pipes for inflow or outflow of cooling gas are provided inside the rotary shaft 33. Cooling gas is introduced into the container 31 from a refrigerant supply device (not shown) separately provided outside to cool the cooling gas. The superconducting coil 35 is configured to be cooled below the critical temperature by gas. The superconducting coil 35 is cooled below the critical temperature, but the normal conducting coil 36 is configured as a normal temperature part. In the superconducting motor 30 of this embodiment, a plurality of superconducting coils 35 are provided, and these need to be electrically connected to each other. Therefore, the plurality of oxide superconducting conductors 1 and 1 constituting each superconducting coil 35 are illustrated in FIG. The connection structure shown in FIG.
As shown in FIG. 5, the superconducting coil 35 arranged around the rotating shaft 33 is formed in a laminated type, and the connection structure shown in FIG. 2 is adopted as the connection structure of the superconducting conductor for constituting the superconducting coil 35. Can do.

  The superconducting motor 30 shown in FIG. 5 introduces a cooling gas into the container 31 and uses the cooling gas to cool the superconducting coil 35 to a critical temperature or lower. A necessary current is supplied to the normal conducting coil 36 from a power supply (not shown) separately, and a necessary current is also supplied to the superconducting coil 35 from a power supply (not shown) separately, thereby rotating due to the magnetic field generated by both coils. The rotating shaft 33 can be rotated by force to be used as a superconducting motor.

The connection structure of the oxide superconducting conductor shown in FIG. 2 can be applied to, for example, a laminated superconducting magnet 40 having the structure shown in FIG. The superconducting magnet 40 of this form has a configuration in which the pancake coils 41 are stacked in eight stages in the example of FIG. 6, and each pancake coil 41 is configured by winding the oxide superconducting conductor 1 in a pancake coil shape. ing.
Thus, in order to connect the plurality of pancake coils 41 of the laminated superconducting magnet 40, the connection structure of the oxide superconducting conductor shown in FIG. 2 can be applied.
For example, when a plurality of pancake coils 41 are connected, the third oxide superconductivity is formed so as to bridge the winding start ends of the oxide superconductors 1 and 1 inside the pancake coils 41 and 41 arranged above and below. A conductor can be arranged and the structure shown in FIG. 2 can be adopted. Further, a third oxide superconducting conductor is disposed so as to bridge the ends of the oxide superconducting conductors 1 and 1 outside the pancake coils 41 and 41 disposed on the upper and lower sides on the winding end side, as shown in FIG. A structure can be adopted.

FIG. 7 shows a second embodiment of the connection structure, in which the first and second oxide superconducting conductors 1 are joined by a conductive joining material 15 with their end portions overlapped by a predetermined length.
In the structure of the second embodiment, since the first and second oxide superconducting conductors 1 are reversed at the joint, this structure can be applied when there is no problem even if the front and back are reversed at the connection.

Also in the structure of the second embodiment, since it is connected by the conductive bonding material 15 having a Young's modulus of less than 41.4 × 10 ⁹ N / m ² , it is applied to a structure in which the superconducting conductors 1 and 1 are wound around a winding drum. Even when bending stress acts on the first and second superconducting conductors 1, the stress acting on the oxide superconducting layer 6 around the connecting portion of the first and second superconducting conductors 1 and 1 is reduced. Therefore, it is possible to provide a connection structure with little deterioration of superconducting characteristics.
Further, the structure of the second embodiment can be applied to the superconducting cable 16 shown in FIG. 3, the superconducting fault current limiter module 25 shown in FIG. 4, the superconducting motor 30, the superconducting magnet 40, the pancake coil 41, etc. Of course.

Al ₂ O ₃ (diffusion prevention layer; film thickness 150 nm) is formed by sputtering on a tape-shaped Hastelloy C276 (trade name, manufactured by Haynes, USA) having a width of 10 mm, a thickness of 100 μm, and a length of 1 m. In addition, Y ₂ O ₃ (bed layer; film thickness 20 nm) was formed by ion beam sputtering. Next, MgO (intermediate layer; film thickness: 10 nm) was formed on the bed layer by ion beam assisted sputtering (IBAD), and then 300 nm thick CeO ₂ (cap layer) by pulsed laser deposition (PLD). ) Was formed. Next, YBa ₂ Cu ₃ O ₇ (oxide superconducting layer) having a thickness of 300 nm is formed on the CeO ₂ layer by a PLD method, and further, an Ag first metal stabilizing layer of 8 μm thickness is formed on the oxide superconducting layer by a sputtering method. To form a tape-shaped superconducting laminate.

Next, a roll prepared by preparing a stabilizing material (thickness 20 μm, width 18 mm) made of Cu tape with 2 μm thick Sn plating on the back surface, vertically attached to one side of the oxide superconducting laminate, and heated to 260 ° C. Was formed into a C shape so as to wrap both ends of the oxide superconducting conductor at both ends in the width direction of the stabilizing material. The oxide superconducting conductor whose sectional structure is shown in FIG. A plurality of oxide superconducting conductors were prepared for the connection test.
In addition, an oxide superconducting conductor having a length of 4.5 cm was obtained by the above-described process, and this was used as a third oxide superconducting conductor for connection. An indium solder layer having a thickness of 40 μm was formed on the surface of the second metal stabilizing layer located on the first metal stabilizing layer with respect to the third oxide superconducting conductor.

Two oxide superconducting conductors are arranged in a line so that the first metal stabilizing layer is located on the upper side with a gap of 5 mm between them, and the third superconducting length of 4.5 cm prepared previously The first metal stabilizing layer of the conductor was disposed so as to cover both ends of each of the two superconducting conductors by 2 cm facing downward. That is, the second metal stabilization layer of the third oxide superconductor is disposed on the second metal stabilization layer of the first and second oxide superconductors.
Next, the indium solder is melted while pressing and pressing the soldering iron on the third oxide superconducting conductor, and then cooled to room temperature to stabilize the third metal against the first and second metal stabilizing layers. The connection structure of the superconducting conductor shown in FIG.

A plurality of linear oxide superconducting conductors connected with the structure shown in FIG. 2 using indium solder were prepared, and these oxide superconducting conductors were subjected to a current test in liquid nitrogen to obtain a critical current (Ic ₀ ).
Next, each winding drum having a radius of 100 mm, 80 mm, 70 mm, 50 mm, 40 mm, 30 mm, and 25 mm is prepared, and the oxide superconducting conductor having the connection structure prepared in the previous step is wound around these winding drums, A test for applying bending stress to the connection structure was performed. When the oxide superconducting conductor was wound around each winding drum, it was wound around the winding drum peripheral surface so that the first and second oxide superconducting conductors were located inside and the third oxide superconducting conductor was located outside.
The whole sample as it is wound on the circumferential surface of the winding drum is immersed in liquid nitrogen, a power source is connected to the ends of the connected first and second oxide superconductors, and the critical current of each sample is measured. (Ic) was measured and compared with the original critical temperature (Ic ₀ ) of the oxide superconducting conductor measured in a linear state before the winding test.

FIG. 8 shows the relationship between the radius (bending radius) of the winding drum and the (Ic / Ic ₀ ) value.
From the test results shown in FIG. 8, the oxide superconducting conductor having a connecting portion using tin solder does not deteriorate when the bending radius is 100 mm or 80 mm, but the critical current value becomes almost zero when the bending radius is 70 mm. I showed the result. This is because the Young's modulus (49.9 GPa) of tin solder is high, and when the bending radius is 70 mm, bending stress concentrates on the soldered portion of the oxide superconducting conductor, and the oxide superconducting layer is damaged by the stress concentration. Seems to be the cause.
On the other hand, the oxide superconducting conductor having a connecting portion using indium solder hardly deteriorated in the critical current value up to a bending radius of 50 mm, 40 mm, and 30 mm, and maintained good superconducting characteristics. In this sample, the critical current value deteriorated only when the bending radius was 25 mm.
From this test result, the use of indium solder with a low Young's modulus improves the bending durability of oxide superconducting conductors with solder joints, and superconducting properties even if the bending radius is reduced compared to the connection structure using tin solder. Was confirmed not to deteriorate.

  The present invention can be used to connect oxide superconducting conductors used in various superconducting devices such as superconducting cables, superconducting magnets, superconducting motors, and superconducting fault current limiter modules.

  DESCRIPTION OF SYMBOLS 1 ... Oxide superconducting conductor, 2 ... Base material, 5 ... Intermediate layer, 6 ... Oxide superconducting layer, 7 ... 1st metal stabilization layer, 8, 8A ... 2nd metal stabilization layer, 9 ... Superconducting lamination | stacking Body, 13 ... third oxide superconducting conductor, 15 ... conductive bonding material, 16 ... superconducting cable, 18 ... superconducting layer, 20 ... superconducting shield layer, 30 ... superconducting motor, 35 ... superconducting coil, 40 ... superconducting magnet, 41 ... Pancake coil, 90 ... Module for superconducting current limiting device, 99 ... Superconducting current limiting device.

Claims (3)

The ends of the first and second superconducting conductors having a structure in which an intermediate layer, an oxide superconducting layer, and a metal stabilizing layer are laminated on a tape-shaped base material are adjacent to each other by overlapping each other's metal stabilizing layers, An overlapping structure of the metal stabilizing layer is joined by a conductive joining material having a Young's modulus of less than 41.4 × 10 ⁹ N / m ² . The ends of the first and second superconducting conductors having a structure in which an intermediate layer, an oxide superconducting layer, and a metal stabilizing layer are laminated on a tape-shaped substrate are mutually on the same side with respect to the substrate. The ends of the adjacent metal stabilizing layers are connected to each other by a third superconducting conductor having a structure in which an intermediate layer, an oxide superconducting layer, and a metal stabilizing layer are laminated on a tape-like base material. It is a connection structure of an oxide superconductor,
The metal stabilization layer of the third superconducting conductor is deposited between the ends of the metal stabilization layers of the adjacent first and second superconducting conductors, and the metal stabilization of the first and second superconducting conductors. And a metal stabilizing layer of the third superconducting conductor are bonded by a conductive bonding material, and the Young's modulus of the conductive bonding material is less than 41.4 × 10 ⁹ N / m ^2. An oxide superconducting conductor connection structure.   A superconducting device provided with the oxide superconducting conductor connection structure according to claim 1.

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